The invention relates to a device for protecting vehicle occupants in a motor vehicle and a method for controlling the inflation of an airbag in a motor vehicle.
The requirements made of the latest devices for protecting vehicle occupants in a motor vehicle go far beyond the simple inflation of an airbag when an impact is detected: a vehicle occupant may possibly be injured by an airbag which is inflated with its full force if, before the inflation or at the start of the inflation, the entire body or individual parts of the body of the vehicle occupant are located in an area which will be occupied several milliseconds later by the volume of the completely inflated airbag. For this reason, it is desirable to determine the position of the vehicle occupant and either to prevent the airbag from being triggered or merely to gently fill an airbag, which can be inflated in multiple stages, if it is detected that the vehicle occupant has moved forward.
A device for detecting the position of a vehicle occupant or of an object on a vehicle seat is disclosed in U.S. Pat. No. 5,413,378. The position of the vehicle occupant is determined through the use of three ultrasonic sensors which are provided in the dashboard, in the backrest of the vehicle seat and Oalong the side of the vehicle seat. The sensors sense a vehicle occupant or an object in the space between the backrest of the vehicle seat and the dashboard. An evaluator determines the position of the vehicle occupant from the sensor signals.
Due to the sensing of the space described above, each ultrasonic sensor must have a range of somewhat more than a meter. This relatively large range causes a relatively low resolution, with the result that distances can be determined with only on a relatively inaccurate scale. For a controlled inflation of the airbag, a high resolution of the distance measurement is necessary. However, on the other hand, it is not necessary to sense every possible position of the vehicle occupant. Furthermore, mounting an ultrasonic sensor in the backrest of the vehicle seat is costly because a passage opening through the cover of the backrest is necessary. Such a configuration of the sensor also adversely affects the sitting comfort.
It is accordingly an object of the invention to provide a device for protecting vehicle occupants in a motor vehicle and a method for controlling the inflation of an airbag which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which, in particular, provide a high resolution along with a simple and cost-effective production.
With the foregoing and other objects in view there is provided, in accordance with the invention, in combination with a motor vehicle including a vehicle seat and a belt device assigned to the vehicle seat, the belt device having an unrolled belt length, a device for protecting a vehicle occupant, including:
an airbag for protecting the vehicle occupant on the vehicle seat, the air bag having a danger area defined by an unfolded, inflated state of the airbag;
a first sensor for detecting a presence of an object or the presence of the vehicle occupant in the danger area;
a second sensor for measuring the unrolled belt length; and
an evaluator, connected to the first sensor, to the second sensor and to the airbag, for controlling an inflation of the airbag as a function of a detection of the presence of the object or the vehicle occupant in the danger area and as a function of the unrolled belt length, the evaluator determining a change in the unrolled belt length based on the unrolled belt length measured at a current time and the unrolled belt length measured at an earlier time.
In other words, a sensor is provided which detects the presence of. an object or of a vehicle occupant in a danger area in front of the airbag. The airbag unfolds as it inflates into the space between the steering wheel or dashboard and the vehicle occupant. The space which the airbag takes up after its inflation constitutes simultaneously a danger area for the vehicle occupant at the time of the inflation. If part of the body of the vehicle occupant is located in this danger area at the time of the inflation, there is a considerable risk of injury by the inflating airbag. With the sensor which is embodied in particular as a distance sensor, only, or at least, the danger area directly in front of the airbag device is sensed, that is to say that area into which the airbag will unfold in the event of an impact. Due to the relatively short range which such a sensor has to have in order to sense the danger areaxe2x80x94in particular less than 40 cm if the sensor is provided, for example, on the dashboardxe2x80x94the scanning or sampling precision is increased, in particular because the algorithm for processing the distance which is determined can be simplified, and therefore more computational power is available for determining distances with a higher scanning or sampling rate. Furthermore, a sensor is provided for the unrolled seat belt lengthxe2x80x94referred to below in abbreviated form as xe2x80x9cbelt lengthxe2x80x9dxe2x80x94of a belt device which is assigned to the vehicle seat. The unrolled belt length and in this context in particular the change in the belt length over time is a measure of the position of the upper part of the body of the vehicle occupant in the vehicle seat. An evaluator controls the inflation of the airbag as a function of the distance determined and the belt length determined. In doing so, the decision that, due to the strength of the impact, the airbag is to be inflated in order to protect the vehicle occupant is usually made by the evaluator as a function of an impact detection devicexe2x80x94for example in the form of an acceleration sensor. However, the evaluator influences this decision to the effect that it determines the degree to which the airbag is to be inflated as a function of the unrolled belt length and as a function of whether an object or a vehicle occupant is detected in the danger area, and at the same time it is also possible to prevent the inflation.
The advantage of the device according to the invention is that the position of the vehicle occupant is detected with high resolution. The resolution-sensitive, relatively weakly irradiating distance sensor and the provision of the further sensor for determining the distance between the vehicle occupant and the backrest of the vehicle seat as a sensor for the unrolled belt length actually provide a device which can be provided at low cost and has a high resolution for the vehicle occupant position which is determined. With these two sensors alone, the vehicle occupant who is sitting in a normal position and leaning against the backrest is distinguished not only from the vehicle occupant who is displaced forward in the direction of the dashboard but also from a vehicle occupant who is, for example, reading a newspaper in a normal sitting position. Furthermore, it is not necessary to make any mechanical interventions in the vehicle seat. In addition, the radiation exposure for the vehicle occupant is greatly reduced. Nevertheless, all the information which is necessary to determine the position of the vehicle occupant, and in particular to be able to distinguish between different positions of the vehicle occupant, is supplied.
In accordance with another feature of the invention, the first sensor for detecting the object or the vehicle occupant in the danger area is an infrared sensor.
In accordance with yet another feature of the invention, an impact detection device is connected to the airbag for detecting an impact. A weight detector is connected to the evaluator for detecting a weight provided on the vehicle seat. The evaluator controls the inflation of the airbag as a function of the impact and as function of the weight.
In accordance with a further feature of the invention, a child""s seat detection device is connected to the evaluator for detecting a child""s seat provided on the vehicle seat and for supplying a status signal. The evaluator controls the inflation of the airbag additionally as a function of the status signal.
In accordance with yet a further feature of the invention, the airbag is inflatable in multiple stages and the evaluator controls the inflation of the airbag by additionally selecting one of the multiple stages.
In accordance with another feature of the invention, the evaluator selectively suppresses and permits the inflation of the airbag in response to an impact. The evaluator permits the inflation of the airbag only to a first volume stage if the object or the vehicle occupant is detected in the danger area and if the unrolled belt length or the change in the unrolled belt length exceeds a limiting value.
In accordance with yet another feature of the invention, the evaluator permits the inflation of the airbag in response to an impact if the object or the vehicle occupant is detected in the danger area and if the unrolled belt length or the change in the unrolled belt length is less than a limiting value.
With the objects of the invention in view there is also provided, a method for controlling an inflation of an airbag in a motor vehicle, which includes the steps of:
detecting, with a first sensor, a presence of an object or a vehicle occupant in a danger area defined by an unfolded, inflated state of an airbag;
detecting, with a second sensor, an unrolled belt length of a belt device assigned to a vehicle seat;
controlling, with an evaluator, an inflation of the airbag as a function of a detection of the object or the vehicle occupant in the danger area and as a function of the unrolled belt length; and
determining, with the evaluator, a change in the unrolled belt length from a currently measured unrolled belt length and a previously measured unrolled belt length.
In accordance with another mode of the invention, the inflation of the airbag due to an impact is selectively suppressed or permitted only to a first volume stage of a plurality of volume stages if the object or the vehicle occupant is detected in the danger area and if the unrolled belt length or the change in the unrolled belt length exceeds respective limiting value.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for protecting vehicle occupants in a motor vehicle and a method for controlling the inflation of an airbag in a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.